Puffed organic material and method of making same



Patented Sept. 22, 1953 PUFFED ORGANIC MATERIAL AND METHOD OF MAKINGSAME John M. Beer, Chicago, 111-, assienor to Guardite Corporation, acorporation of Delaware No Drawing. Application June 12, 1953, SerialNo. 361.415

18 Claims.

This invention relates to the pulling of organic materials.

The present application is a continuation-inpart of my copendingapplication, Serial No. 296,963, filed July 2, 1952, now abandoned,which in turn is a continuation-in-part of my applications, Serial No.40,630, filed July 24, 1948, now abandoned, and copending Serial No.189,679, filed October 11, 1950, now abandoned. My application, SerialNo. 189,679, filed October 11, 1950, was a continuation-in-part of myfollowing applications: Serial No. 34,821, new abandoned; Serial No.34,822, now abandoned; and Serial No, 34,823, now abandoned, all filedJune 23, 1948; Serial No. 23,869, filed April 28, 1948, now abandoned;Serial No. 38,179, filed July 10, 1948, now abandoned; and Serial No.40,630, filed July 24, 1948, now abandoned.

Reference is had to the related cases of John M. Baer and Frank B.Doyle, Serial No. 62,984, filed December 1, 1948; Allison and Carmen,Serial No. 161,744, filed May 12, 1950, now abandoned; Carman andAllison, Serial No. 259,313, filed November 30, 1951, now abandoned; andCarman and Allison, Serial No. 275,458, filed March 7, 1952, nowabandoned.

The problem of pulling organic materials and particularly organiccellular materials, involves a large number of interlocking variables.In the first place, the material, itself, must be sufiiciently elasticthat it can be pulled. It must have cells or other divisions within itwhich will trap expanding gas and thus provide the pressure differentialnecessary for pulling. A sudden drop in pressure must be provided ofsuch amount to produce the pressure difference necessary not only toexpand the cell walls but to do so in spite of the leakage thatnecessarily occurs. On the other hand, the pressure difference must begreat enough to exceed the elastic limit of the material before puflinghas occurred. The expansability of the cell wall normally depends uponthe moisture content 01' the product, the condition of that moisture asto being free or combined, the temperature of the article and itschemical condition, particularly as to whether it is cooked or uncooked.

Likewise, there must not only be the pressure difference required toinstitute putting, but there must be a volumetric increase of the gasesinvolved sumcient to maintain it.

I have now found that another factor involved, which has hitherto beencompletely overlooked but the accomplishment of which is inherent in theoperation described in my previous applications referred to, is thatonce the article has been pulled, the pufied condition must bemaintained even after the pressure diflerence has been removed. One ofthe difllculties encountered in many instances of pulling in the priorart was that an article could be puffed, but after pulling wouldcollapse because of the weakened condition of the walls following theleakage out of the gas which produced pumng. This was particularly trueif, after pufllng, the pressure outside of the puffed article wasincreased.

I have now found that by suddenly cooling and dehydrating the product sothat its final temperature is below 150 F. and preferably well below lt-as for example, from 32 F. or lower up to, say, 100 F., that the cellwalls of the prod-' not on pufling are cold set so that on standing oron the application of pressure, even of a greatly increased amount,collapse does not occur.

These results are obtained automatically by following the proceduresalready outlined in my previous applications. In these procedures, thefollowing points are important:

1. Substantially all of the air should be removed from the product andreplaced by an atmosphere of steam prior to pulling.

2. The product should be cooked by steam or otherwise or moistenedpreferably by the addition of substantially air-free steam at higherpressure and temperature until the condition of the material is properfor pulling and its moisture content is within the desired range. Theuse of the process permits the introduction of substantially moremoisture than was permissible under the old processes.

3. It is preferred that the sudden release of pressure be into amaintained vacuum zone which is initially below eight inches of mercuryabsolute.

The conditions of the resulting explosion should be such as to causecold setting of the pulled product. This means that in actual practice,employing commercially practicable vacuum equipment, the pressure mayride up somewhat during the pulling step. It is preferred to continueevacuation of the vacuum zone during the pufling step so as to causecold setting of the pulled product. The expansion of air-free steam intoa vacuum of four inches of mercury absolute will automatically reducethe temperature of the product to approximately F. Reduction of thepressure to two inches reduces the temperature approximately to 100 F.Reduction to one inch reduces it to about 79 F. and reduction to 0.2inch reduces it to approximately 34 F.

Furthermore. by pulling into a maintained vacuum zone, it is possible toobtain a greater temperature drop in number of degrees between themaximum and minimum than was ordinarily obtainable heretofore. Theresult of this greater temperature drop was to permit the evaporation ofmore water from the product by boiling. This boiling not only maintainedthe pressure difference for pulling, but the removal of the water helpedto cold set the cell walls by reducing plasticity and elasticity. Thecombination of the moisture reduction plus chilling, particularly below100 F., has produced results not heretofore obtainable.

In a vacuum process, this reduction of temperature is of particularsignificance, since the lower the vacuum used the greater is theincrease in pressure after the completion of the pufling operation whenthe material is taken back into the atmosphere. If it were not for thecooling and drying effects, many products would not be able to maintaintheir pufied condition when the pressure is increased, for example fromtwo inches absolute to thirty inches absolute-an increase offifteenfold.

The removal of the air from inside the organic material in the firstinstance has a number of advantages. In the first place, the oxygen ofthe air has a deleterious efiect on many products, particularly whenthey are heated. Secondly, the removal of non-condensable gasesincreases the permeability of the material to heat and to steam so thatheating will occur uniformly and the steam will penetrate equally to allportions of the material.

Thus, when it comes to introducing steam for increasing the moisturecontent of the product and for cooking it to the necessary chemical andphysical conditions, the fact that air is not present inside the or anicmaterial produces a rapidity and uniformity of steaming and cooking nototherwise possible. Because of this greater uniformity and speed, it ispossible to go to higher temperatures and pressures than would otherwisebe possible. Normally, however, it permits the use of lower temperaturesand pressures than otherwise required. As an example of this, raw wheathaving a weight of 188 grams per unit of volume (one cup) approximately,was subjected to a series of tests. Various samples of the wheat werecooked for fifteen minutes at thirtyfive pounds gauge of steam pressure,in each case after removing substantially all of the air from thegrains.

In the first group of tests, pressure was then increased to 100 poundswith steam held for fifteen seconds and the product then pulled to thefull chamber vacuum of approximately 0.2 inch of mercury absolute. Theweight of the material per cup dropped from an average of 188.5 grams(average of five samples) to 18.7 grams (average of five samples) Thefollowing table shows the weights before and after pufilng of fivesamples oi wheat.

On the other hand, in the second group of tests after the cooking, thesteam was replaced by 100 pounds of air pressure which was held for v 4fifteen seconds and then the material pulled to the same full chambervacuum. In this, the five original samples had the same average weightas before but the average weight per cup after pufling, instead of being18.7 grams was 150 grams for the five samples.

On the other hand. wheat cooked in the same manner for the same timeand-then having the pressure raised to 115 pounds with steam air-free.held for fifteen seconds and then puffed to atmosphere showed an averagefinal weight per cup o1 60.1 grams for five samples as compared to the18.7 when pufled to the vacuum. 115 pounds was used here in order tohave the same pressure diflferences as in the first one in which thepound pressure was pufled to full vacuum.

The actual pressure to be employed before pulling will vary depending onthe particular product concerned. With many products, temperature is avery important factor and since with saturated steam, free from air, thetemperature of the product is directly dependent upon the pressure, itfrequently is desirable to use the minimum temperature and pressurepossible. Thus, some products may be pufi'ed without exceedingatmospheric pressure at the time of the puff, and in some cases thepulling pressure may be puiied without exceeding atmospheric pressure atthe time of the puff, and in some cases the puiling pressure may beactually sub-atmospheric.

On the other hand, for inorganic materials like vermiculite. the uppertemperature is usually unimportant.

Tobacco is an example of a material which is extremely heat sensitive,although some kinds of tobacco are less so, and the stem portions aregenerally less so than the leaf portions of the stem.

The Doyle patent, No. 2,627,221, which issued February 3, 1953, shows apufling apparatus particularly suitable for carrying out the processesherein described. In such an apparatus a steaming chamber is providedwithin which the product may be placed. This steaming chamber isconnected by a triggered door to an expansion chamber. The expansionchamber is preferably kept at a very low pressure, means being providedto maintain a low pressure during the pulling. The steaming chamber isprovided with evacuating means, steaming means, and usually with a purgeline through which non-condensible gases can be eliminated as well assome condensed steam which is developed during steaming.

As an example of the process. durum wheat was introduced to the steamingchamber. Air and other non-condensible gases were removed from the wheatgrains by reducing the pressure in the steaming chamber to about 0.2inch of mercury absolute while withdrawing the generated steam.Saturated steam was then introduced and the pressure increased to 35pounds gauge, and held at this point for fifteen minutes tosubstantially completely cook the material without loss of cellularidentity. The steam pressure was then raised to 100 pounds per squareinch gauge, held for 15 seconds, following which the wheat was firedinto the expansion chamber which in this instance was at a pressure of0.2 inch of mercury absolute. This firing is done by suddenly releasingthe triggered door of the expansion chamber and the resulting explosionejects the wheat into the expansion chamber. The potentiometer indicateda temperature at the moment of the pun at slightly below 32 F.indicating an actual super-cooling of the material.

The actual values of the variables in the cooking-pufling cycles of thismethod depend upon the condition and type of material being used, aswell as the degree of putting desired.

The extent of the puffing secured may be varied in a number of ways. Themoisture content of the product is one factor. Its temperature isanother. Its physical condition as a result of cooking is another. Thepressure employed is another. Products which have been pulled to thesame extent are by no means necessarily alike in their physical,chemical. and taste properties. Particularly important is the ability torehydrate. which may be very much different for two particles ofinherently the same size. This does not mean that a predeterminedproduct may not be produced. Using the same base material and treatingit in the same way will produce on all occasions a substantiallyidentical product.

As a further example of the process. tobacco stems which had beenredried in a conventional manner and then stored until they were dry tothe touch and were brittle, were first moistened, preferably in thepulling apparatus, until they were slightly pliable. At the conclusionof the moistening operation, the particular stems were in an atmosphereof steam under a pressure of approximately two inches of mercuryabsolute. They were then subjected to an increasing steam pressure untilthe temperature had risen 180 to 250 F., corresponding to about eightpounds to thirty pounds absolute. The material was then pulled byopening of the triggered door into the explosion or expansion chamber ata pressure of approximately 0.2 inch of mercury absolute, which pressurewas maintained during the operation. as in the previous cases, byoperation of the evacuation system in the expansion chamber during thepulling. Because of this operation, the pressure was not permitted torise above approximately one inch of mercury absolute during pufling.Similar operations have been carried out upon leaf tobacco suitablymoistened before the operation. In the case of leaf tobacco. thepressure difference and other conditions should not be such as toshatter the leaves unduly.

In another operation, green tobacco, that is tobacco which had not beenredried, was placed in loose hands in the steaming chamber. Air was thenremoved by production of a vacuum to a point at which water would boilfrom the tobacco. The pressure at this point was 0.2 inch of mercuryabsolute which was held for four minutes after which steam wasintroduced to raise the pressure to 20 pounds gauge and this was heldfor two minutes. The trigger was then pulled and the material puiIedinto the expansion chamber which was at 0.2 inch of mercury absolute andwhich was maintained at a low pressure by continued evacuation.

Preferred moisture content for the tobacco is upwards of 13% andnormally from 14% to 18% before pulling and, in fact, before thesteaming operation. With redried tobacco, higher pressures such as to 00pounds gauge may be employed.

In the case of starchy products such as wheat, the cooking and moisturecondition of the material have a more profound effect than in productslike tobacco.

In thelcase of rice, the rice grains in their dried state may beemployed without moistening. However, in some instances it may bedesired to supply flavor, and/or moistening, and/or nutritional valuesto the grain prior to, during, or after pulling. This may be done by theuse of a liquid carrier,-such as water. under high temperature andpressure which is exploded into the vessel maintaining the product underhigh vacuum in an atmosphere of steam. By using water under a pressureand temperature corresponding to that. of say, 100 pounds gauge ofsteam, the particles may be exploded into a fine mist which willpenetrate the grains, particularly after they have been pulled. In'thisway moisture, sugar, salt, certain vitamins, and nutritional salts maybe supplied to the material with or without other flavoring agents. Thismay be done immediately following the initial evacuation (i. e., duringcooking) or immediately following the pufling. It is less economical todo it at some intermediate stage.

The rice should be thoroughly cooked for desirable pulling. I have foundthat cooking at 20 pounds steam pressure gauge for about five to sevenminutes produces satisfactory results. Following cooking in the steamingchamber, the steam pressure was increased rapidly; for example, inthirty seconds to a pressure of pounds gauge or higher, as for example,pounds gauge, after which the pressure was immediately (andinstantaneously) reduced to subatmospheric, preferably below eightinches of mercury absolute and particularly to about 0.2 inch of mercuryabsolute. This was done by opening the triggered door of the puflingapparatus and firing the rice into the expansion chamber. The pressurewithin the expansion chamber was maintained at a low point by continuingthe evacuation during the puffing and normally the pressure in thatchamber was not permitted to exceed four inches of mercury absolute andpreferably not permitted to exceed two inches of mercury absolute. Insome instances, however, I have operated successfully with the pressurein the expansion chamber following explosion riding up to as high as 4to 8 inches of mercury absolute as measured on a standard mercurymanometer, but in most instances the pressure was reduced below 4 inchesof mercury absolute within a few minutes and before reimposition ofatmospheric pressure.

The actual values of the variables in the cooking-pufllng cycles of thismethod depend upon the condition and type of rice being used, as well asthe degree of putting desired.

The resulting vacuum pufled rice has a volume of from about 6 to 12times the original kernels as determined by their cup weights. Putconversely, the specific gravity, as determined from cup weights, isfrom 8%% to 16%% of the specific gravity of the original kernels. Theshape of the original kernels is maintained, although greatly enlarged.On cross-section, some of the vacuum puffed rice kernels will be foundto have a small central hollow spot, but this is relatively smallcompared to previously puffed rice. The average cell size appears to befrom one fifth to one tenth the diameter of the usual puffed material.The cell walls are glassy or vitreous in appearance, and give a snowwhite appearance to the inside of the grain, although apparently thewalls are transparent. Under magnification the interior of the grainresembles a snow field. The exterior of the pulled rice grain is notcase hardened, and upon wetting, water is immediately and instantlyabsorbed throughout. After soaking in water at 65 F. for about 10minutes, the vacuum pufled rice grains retain their entity and shape anddo not break up even when mashed down on a microscopic slide, whereas acorresponding commercially puffed rice soaked under the same conditionsis collapsed and when mashed down on a microscopic slide the tissuebreaks down completely. When iodine is added to the vacuum puffed ricegrains soaked in water at 65 F. for10 minutes, there is substantiallylittle or no change in its color, indicating that under this condition,the starch is substantially water insoluble. Iodine added tocommercially pufl'ed rice grains under the same conditions immediatelychanges color on contacting the water, indicating that the starch ofsuch rice is water soluble under similar conditions.

By "commercially puffed rice I mean a commercially available puffed riceproduced by the stand rd prior art processes such as Warren Patent No.2,261,456.

Examples of applying the method of this invention to rice are:

Example 1 Short-grained Arkansas Riceland 500" rice (15 pounds) wasplaced in the steam chamber, subjected to a pressure of 1.5 inches ofmercury absolute for 2 minutes, the rice being at a temperature of about91 F., to remove substantially all of the non-condensable gases from therice grains. The rice was then steamed quickly to a steam pressure of 20pounds per square inch gauge, held at this pressure for 7 minutesaccompanied by continual purging of the steam, steamed to 100 pounds persquare inch gauge, held at this pressure for 15 seconds, and then firedinto the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute. Evacuation of the expansion chamber was continuedduring the puff until the grains were cold set.

Example 2 15 pounds of rice were treated in the same manner as inExample 1, except that the step of subjecting the rice to 1.5 inches ofmercury absolute for 2 minutes prior to steaming was omitted.

Example 3 Arkansas Riceland rice (15 pounds) was placed in the steamchamber and the pressure reduced to 1.5 inches of mercury absolute for 2minutes, the rice being at a temperature of about 91 F., to removesubstantially all of the non-condensable gases. The rice was thensteamed to a pressure of 20 pounds per square inch gauge in 5 minutes,held there for 2 minutes, steamed to 100 pounds per square inch gauge in5 minutes, held there for 2 minutes, following which the pressure wasdecreased to 80 pounds gauge, held there for 15 seconds, and the ricethen fired into the expansion chamber which was at a pressure of 0.2inch of mercury absolute. Evacuation of the expansion chamber wascontinued during the pull until the grains were cold set.

The puffed rice grains from Examples 1 and 2 were very satisfactoryhaving the above described characteristics. However, when a sample ofrice was treated in the same manner as described in Example 1 exceptthat the steps of subjecting it to 1.5 inches of mercury absolute priorto steaming and of purging during steaming were both omitted, i. e., thenon-condensable gases were not removed prior to vacuum pufllng, theresulting puffed rice grains were a total loss, as over of them werereduced to fines similar to brewers grits. This indicates the importanceof removing the non-condensable gases from the rice grains prior topulling.

A sample of the vacuum puffed rice of Example 3 above showed 50%nitrogen efliciency as compared to a negative emciency by a commerciallypuifed rice.

In the case of wheat, the wheat grains in their normal dry state may beemployed without moistening. However, in some instances it may bedesired to supply flavor, and/or moistening. and/or nutritional valuesto the grain, prior to, during, or after putting. This may be done inthe same manner as previously described in the case 01' rice.

The wheat should be thoroughly cooked for desirable pulling. I havefound that cooking at from about 35 to pounds steam pressure gauge for aperiod of from about 1 to 15 minutes produces satisfactory results.Following cook,- ing in the steaming chamber, the steam pressure wasadjusted to form about 35 to 100 pounds gauge, after which the pressurewas then immediately (and instantaneously) reduced to subatmospheric,preferably below 8 inches of mercury absolute and particularly to about0.2 inch of mercury absolute. This was done by opening the triggereddoor of the pufflng and tiring the wheat into the expansion chamber. Thepressure within the expansion chamber was maintained at a low point bycontinuing the evacuation during the pufling and normally the pressurein that chamber was not permitted to exceed 4 inches of mercury absoluteand preferably not permitted to exceed 2 inches of mercury absolute. Insome instances, however, I have operated successfully with the pressurein the expansion chamber following explosion riding up to as high as 4to 8 inches of mercury absolute as measured on a standard mercurymanometer, but in most instances the pressure was reduced below 4 inchesof mercury absolute within a few minutes and before reimposition o1atmospheric pressure.

The actual values of the variables in the cooking-puiilng cycles of thismethod depend upon the condtion and the type of wheat being used as wellas the degree of pulling desired.

The resulting vacuum puiied wheat has a volume of from about 4 to 10times the original grains, as determined by their cup weights. Putconversely, the specific gravity as determined by cup weights is fromabout 10% to 25% of the specific gravity oi the original wheat grains.The vacuum pufled wheat particles are everted. substantially pure whiteexcept for the bran particles adhering thereto, and are entirelydifferent in shape from the original wheat grains. The cellularstructure is vitreous in appearance. On cross-section, the pufled grainshave a large number of relatively large carvities substantiallyuniformly distributed throughout the interior. These cavities while byno means spherical are generally rounded at their protuberances.

The vacuum pufl'ed wheat grains are immediately wettable by water,except in those portions protected by the bran fragments and whenimmersed in water at 65 F., for a period of 10 minutes, they retaintheir entity and shape and do not break down even when mashed on amicroscopic slide.

assaoos Examples of applying the method or this invention to wheat are:

Example 4 Red durum wheat was placed in a steam chamber which was thenevacuated to an absolute pressure or about 0.2 inch oi mercury absolute,the temperature of the wheat being not less than about 40 F., to removesubstantially all oi the non-condensable gases. The wheat was thensteamed to a pressure or 35 pounds per square inch gauge, held there for8 minutes accompanied by continual purging oi the steam, quickly steamedto 100 pounds gauge. held there for about 15 seconds, and then ilredinto the expansion chamber which was at a pressure 0.2 inch of mercuryabsolute. Evacuation ot the expansion chamber was continued during thepull until the grains were cold set.

Example Red durum wheat (15 pounds) were placed in the steam chamber andthe pressure reduced to about 0.2 inch 01 mercury absolute for 2minutes, the wheat being at a temperature 01 not less than 40 F., toremove substantially all of the non-condensable gases from the wheatgrains. The wheat was then steamed to a pressure of 100 pounds persquare inch gauge. held there for 2 minutes accompanied by co tinualpurging oi the steam, and then fired into the expansion chamber whichwas at a pressure of 0.2 inch of mercury absolute. Evacuation of theexpansion chamber was continued during the pull until the grains werecold set.

Example 6 Red durum wheat (5 pounds) was placed in the steam chamber andthe pressure reduced to 0.2 inch of mercury absolute for 2 minutes, thewheat being at a temperature not less than about 40 F.. to removesubstantially all of the noncondensable gases. The wheat was thensteamed to '75 pounds per square inch gauge in V2 minute. held there for1 minutes accompanied by continual purging of the steam. and then firedinto the expansion chamber which was at a pressure oi 0.2 inch ofmercury absolute. Evacuation of the expansion chamber was continuedduring the pull until the grains were cold set.

Example 7 Wheat (5 pounds) was placed in the steam chamber and thepressure reduced to 0.2 inch of mercury absolute for 2 minutes, thewheat being at a temperature not less than 40" F., to removesubstantially all of the non-condensable gases. The wheat was thensteamed to a pressure of '15 pounds per square inch gauge, held therefor 4 minutes accompanied by continual purging o! the steam, and thenfired into the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute. Evacuation of the expansion chamber was continuedduring the pull until the grains were cold set.

Example 8 Red durum wheat (20 pounds) was placed in the steam chamberand the pressure reduced to about 0.2 inch of mercury absolute for 2minutes, the wheat being at a temperature not less than about 40 F., toremove substantially all of the non-condensable gases. The wheat wasthen steamed to a pressure of 100 pounds per square inch gauge, heldthere ior 5 minutes. following which the steam pressure was quicklyreduced to 10 50 pounds per square inch gauge, and then the wheat wasfired into the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute. Evacuation oi the expansion chamber was continuedduring the puff until the grains were cold set.

Example 9 Wheat was treated in the same manner as in Example 4 exceptthat in the step of removing the non-condensable gases from the wheatgrains prior to steaming, the period of evacuation at 0.2 inch ofmercury absolute pressure was 1 minute instead 0! 2 minutes.

Example 10 Wheat was treated in the same manner as in Example 4 exceptthat in the step of removing the non-condensable gases from the wheatgrains prior to steaming, the period 0! evacuation at 0.2 inch ofmercury absolute pressure was 5 minutes instead of 2 minutes.

Example 11 Wheat (20 pounds) was placed in the steam chamber and thepressure reduced to 0.2 inch oi mercury" absolute for 2 minutes, thewheat being at a temperature not less than about 40 F., to removesubstantially all of the non-condensable gases. The wheat was thensteamed at a pressure of 100 pounds per square inch gauge in seconds,held there tor 5' minutes and then fired into the expansion chamberwhich was at a pressure or 0.2 inch oi mercury absolute. Evacuation oithe expansion chamber was continued durin the pull until the grains werecold set.

The pulled wheat grains irom Examples 4 to 11 were very satisfactory,having the above described characteristics. Samples of the vacuum pufledwheat from these examples showed from 11% to 15% thiamine retention and78% to 87% lysine retention. A standard commercial pulled wheat showed 0thiamine retention and 35% lysine retention. The sample from Example 9had the 11% thiamine retention determination and that from Example 10had the 15% thiamine retention determination.

The lysine retention was likewise greater tor the vacuum pufled wheatproduct which had been evacuated for 5 minutes before steaming, i. e..Example 10.

The pulled wheat product produced by the process of this method showed51% nitrogen emciency by a feed test compared to a negative emciency tora corresponding commercially pulled wheat.

In the case oi iarina or wheat middlings, rarina in its normal dry statemay be employed without moistening. However, in some instances it may bedesired to supply flavor, and/or molstening and/or nutritional value tothe grain, prior to, during, or after pulling. This may be done in thesame manner as previously described in the case of rice.

The Karina should be thoroughLv cooked for desirable pufling. I havefound that cooking at from 40 to pounds steam pressure gauge for aperiod of about 2 minutes produces satisfactory results. Followingcooking, the steam pressure was adjusted to irom 40 to 100 pounds gauge,alter which the pressure was then immediately reduced tosub-atmospheric, preferably below 8 inches oi. mercury absolute andparticularly to about 0.2 inch of mercury absolute. This was done byopening the triggered door of the puihng apparatus and firing the tarinainto the expansion chamber. The pressure within the expansion chamberwas maintained at a low point by continuing the evacuation during thepuiflng and normally the pressure in that chamber was not permitted toexceed four inches of mercury absolute and preferably not permitted toexceed 2 inches of mercury absolute. In some instances, however, I haveoperated successfully with the pressure in the expansion chamberfollowing explosion riding up to as high as 4 to 8 inches of mercuryabsolute as measured on a standard mercury manometer, but in mostinstances the pressure was reduced below 4 inches of mercury absolutewithin a few minutes and before reimposition of atmospheric pressure.

The actual values of the variables in the cooking-puifing cycles oi thismethod depend upon the condition and the type of wheat middlings beingused as well as the degree of pufing desired.

The resulting vacuum pulled farina has a volume of from about 4 to 8times the original farina particles as determined by cup weights. Putconversely, the specific gravity as determined by cup weights is fromabout 12%% to 83%% of the specific gravity of the original farinaparticles. The shape of the original particles is roughly maintainedalthough the outer surface or the puffed material is rough. The productis not case hardened so far as can be observed. The vacuum pufled farinais not transparent but is translucent. having a milky-white appearance.

Examples of applying the method of this invention to rarina are:

Example 12 Farina pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farina being at a temperature not less than about 40 F., to removesubstantially all of the noncondensable gases. The farina was thenquickly steamed to a pressure of 75 pounds per square inch gauge, heldthere for 2 minutes accompanied by continual purging of the steam, andthen fired into the expansion chamber which was at a pressure of 0.2inch of mercury absolute. Evacuation of the expansion chamber wascontinued during the puii' until the farina particles were cold set.

Example 13 Farina (5 pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farina being at a temperature not less than about 40 F., to removesubstantially all of the noncondensable gases. The farina was thenquickly steamed to a pressure oi 60 pounds per square inch gauge, heldthere for 2 minutes accompanied by continual purging of the steam, andthen fired into the expansion chamber which was at a pressure of 0.2inch of mercury absolute. Evacuation of the expansion chamber wascontinued during the puff until the farms particles were cold set.

Example 14 Farina (5 pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farms. being at a temperature not less than about 40 F., to removesubstantially all of the noncondensable gases. The iarina was thenquickly steamed to a pressure of 40 pounds per square inch gauge, heldthere for 2 minutes accompanied by continual purgin of the steam,quickly steamed to 75 pounds per square inch gauge, and then fired intothe expansion chamber which was at a pressure of 0.2 inch of mercuryabsolute. Evacuation of the expansion chamber was con tinued during thepull until the iarina particles were cold set.

Example 15 Farina (5 pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farina being at a temperature not less than about 40 F., to removesubstantially all of the non-condensable gases. The farina was thenquickly steamed to a pressure of pounds per square inch gauge, heldthere for 2 minutes accompanied by continual purging of the steam, andthen fired into the expansion chamber which was at a pressure of 0.2inch of mercury absolute. Evacuation oi the expansion chamber wascontinued during the pufi until the farina particles were cold set.

Example 16 Farina (20 pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farina being at a temperature not less than about 40 F., to removesubstantially all of the non-condensable gases. The iarina was thensteamed to a pressure of 50 pounds per square inch gauge. held there for2 minutes, quickly steamed to 70 pounds gauge, and then fired into theexpansion chamber which was at a pressure of 0.2 inch of mercuryabsolute. Evacuation of the expansion chamber was continued absoluteduring the pull. until the farina particles were cold set.

Example 17 Farina (20 pounds) was placed in the steam chamber and thepressure reduced to about 0.2 inch of mercury absolute for 2 minutes,the farina being at a temperature not less than about 40 F., to removesubstantially all of the non-condensable gases. The farina was thenquickly steamed to a. pressure of 40 pounds per square inch gauge in 30seconds, held there for 2 minutes accompanied by continual purging ofthe steam, and then fired into the expansion chamber which was at apressure of 0.2 inch of mercury absolute. Evacuation of the expansionchamber was continued during the pull until the farina particles werecold set.

When the vacuum puffed farina prepared in the manner described above ismixed with cold or hot milk, it is ready for consumption within /zminute or less. Thus, this vacuum pufled farina is a ready-to-eatcereal.

A number of runs were made to determine the rate of hydration of thevacuum pulled farina of this invention. For each run, the hydrationdeterminations were made using gram samples. One sample of each run wasplaced in a container having one quart (946 grams) of water maintainedat about 70 F. After 1, 5. 10, and 20 minute intervals, the water-farinamixture was poured into a strainer while substantially all of the freewater passed into a measuring cup in from 10 to 20 seconds. Afterweighing the free water, it and the iarina were again placed in thecontainer. The difference in weight between the free water in thecontainer just prior to placing the farina sample therein and the weightof free water at each time interval was the amount of water absorbed bythe farina at that particular time.

It was found that the amount of water absorbed by the vacuum pufledfarina was more than 400% of the original dry weight of the a,ssa,oas

13 farina after minutes. when compared with the hydration of commercialfarinas, the farina product of this invention absorbs approximately 3%times as much water at the end of 5 minutes than a commercial farinaunder the same conditions.

In the case of oats. the cat grains in their normal dry state may beemployed without moistening. However, in some instances it may bedesired to supply flavor, and/or moistening. and/ or nutritional valuesto the grain, prior to, during, or after putting. This may be done inthe same manner as previously described in the case of rice.

The cats should be thoroughly cooked for desirable mm. 1 have found thatcooking at from 50 to 100 pounds steam pressure gauge for a period offrom about 4 to 18 minutes produces satisfactory results. Followingcooking. the steam pressure was adjusted to from '15 to 100 poundsgauge, after which the pressure was then immediately reduced tosub-atmospheric, preferably below 8 inches of mercury absolute andparticularly to about 0.2 inch of mercury absolute. This was done byopening the triggered door of the pulling apparatus and firing the oatsinto the expansion chamber. The pressure within the expansion chamberwas maintained at a low point by continuing the evacuation during thepulling and normally the pressure in that chamber was not permitted toexceed four inches of mercury absolute and preferably not permitted toexceed 2 inches of mercury absolute. In some instances. however. I haveoperated successfully with the pressure in the expansion chamberfollowing explasion riding up to as high as 4 to 8 inches of mercuryabsolute as measured on a standard mercury manometer, but in mostinstances the pressure was reduced below 4 inches of mercury absolutewithin a few minutes and before reimposition of atmospheric pressure.

The actual values of the variables in the cooking-pufling cycles of thismethod depend on the condition and type of cats being used as well asthe degree of putting desired.

' The resulting vacuum pufled cats have a volume of from about 4 to 8times the original grains as determined by their cup weights. Putconversely, the specific gravity as determined by cup weights is about12%? to 25% of the specific gravity of the original oat grains. Thevacuum pufled oat grains are everted, substantially pure white exceptfor the bran particles adhering thereto, and are entirely dlflerent inshape from the original oat grains. The cellular structure is vitreousin appearance and the product is iminediately wettable by water exceptfor those portions protected by the bran fragments which adhere to thepufled oat particle.

The vacuum pulled oats, pulled according to the method of thisinvention, may be stored for long periods of time under atmosphericconditions without becoming rancid. Samples have been stored incontainers for periods of from 3 to 6 months under atmosphericconditions without turning rancid.

Examples of applying the method of this invention to oats are:

Example 18 Hulled oats pounds) were placed inthe steam chamber and thepressure reduced to about 02 inch of mercury absolute for 2 minutes, theoats being at a temperature not less than about 40 F., to removesubstantially all of the noncondensable gases. The oats were thensteamed to a pressure of 100 pounds per square inch gauge, held therefor 6 minutes accompanied by continual purging of the steam. and thentired into the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute. Evacuation of the expansion chamber was continuedduring the puff until the cat grains were cold set.

Example 19 Hulledoats (10 pounds) where treated in the same manner as inExample 18, except that in the steaming and puihng cycles, the oats weresteamed to pounds per square inch gauge, held there for 15 minutes,steamed quickly to 100 pounds per square inch gauge, held there for 2minutes, and then fired into the expansion chamber.

Example 20 Hulled oats (10 pounds) were treated in the same manner as inExample 18, except that in the steaming and pumng cycles, the oats weresteamed to pounds per square inch gauge, held there for 15 minutes,quickly steamed to 100 pounds per square inch gauge, held there for 8minutes. and then fired into the expansion chamber.

Example 21 Hulled oats (10 pounds) were treated in the same manner as inExample 18, except that in the steaming cycle the oats were steamed to apressure of 100 pounds per square inch gauge and held there for 8minutes instead of 6 minutes.

Eaample 22 Hulled cats (35 pounds) were treated in the same manner as inExample 18, except that in the steaming cycle the cats were steamed to apressure of 100 pounds per square inch gauge and held there for 4minutes instead of 8 minutes.

Example 23 Hulled cats (in pounds) were treated in the same manner as inExample 18, except that in the steaming cycle the oats were steamed to apressure of 100 pounds per square inch and held there for 10 minutesinstead of 6 minutes.

Example 24 Hulled cats (10 pounds) were treated in the same manner as inExample 18, except that in the steaming and pulling cycles the oats weresteamed to apressure of 100 pounds per square inch gauge. held there for6 minutes accompanied by continual purging of the steam, following whichthe steam pressure was reduced to pounds per square inch gauge, heldthere for 15 seconds, and then fired into the expansion chamber whichwas at a pressure of 0.2 inch of mercury absolute.

Example 25 Hulled oats (10 pounds) were treated in the same manner as inExample 18, except that in the steaming and pumng cycles the cats weresteamed to a pressure of pounds per square inch gauge, held there for 6minutes accompanied by continual purging of the steam, and then iiredinto the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute.

Example 26 Hulled oats (20 pounds) were treated in the same manner asExample 18, except that in the steaming and pufling cycles the oats weresteamed aesaoos 15 to a pressure of 100 pounds per square inch gauge in2 minutes, held there for 5 minutes accompanied by continual purging ofthe steam, and then fired into the expansion chamber which was at apressure of 0.2 inch of mercury absolute.

Example 27 Hulled cats pounds) were treated in the same manner asExample 18, except that in the steaming and pulling cycles the oats weresteamed to a pressure of 55 pounds per square inch gauge in minutes,quickly steamed to 100 pounds gauge, held there for 1 minute, and thenfired into the expansion chamber which was at a pressure of about 0.2inch of mercury absolute.

Example 28 Hulled cats (10 pounds) were treated in the same manner asExample 2'1, except that in the steaming and pulling cycles the catswere subjected to a pressure of 100 pounds per square inch gauge for 6minutes instead of 1 minute, and then fired into the expansion chamberwhich was at a pressure of about 0.2 inch of mercury absolute.

Pulled oats are not commercially available and therefore no comparisonscan be made. However, a puffed oat prepared by the present process byfreeing from air, steaming at 55 pounds gauge for 15 minutes, raising to100 pounds gauge, holding there for 1 minute, and then pufiing to asubstantial vacuum showed 62% lysine retention.

Another vacuum pufl'ed oat product similarly prepared except that it washeld at 100 pounds gauge for 6 minutes showed 65% lysine retention.

In the case of corn and particularly corn grits, or hominy, corn gritsin their normal dry state may be employed without moistening. However,in some instances it may be desired to supply flavor, and/or moistening,and/or nutritional values to the grain, prior to, during, or afterpulling. This may be done in the same manner as previously described inthe case of rice.

The corn grits should be thoroughly cooked for desirable pulling. I havefound that cooking at from 70 to 100 pounds steam pressure gauge for aperiod of from about 1 to 11 minutes produces satisfactory results.Following cooking, the steam pressure was adjusted to form 60 to 100pounds gauge, after which the pressure was immediately reduced tosub-atmospheric pressure, preferably below 8 inches of mercury absoluteand particularly to about 0.2 inch of mercury absolute. This was done byopening the triggered door of the puillng apparatus and firing the corngrit into the expansion chamber. The pressure within the expansionchamber was maintained at a low point by continuing the evacuationduring the pulling and normally the pressure in that chamber was notpermitted to exceed four inches of mercury absolute and preferably notpermitted to exceed 2 inches of mercury absolute. In some instances,however, I have operated successfully with the pressure in the expansionchamber following explosion riding up to as high as 4 to 8 inches ofmercury absolute as measured on a standard mercury manometer, but inmost instances the pressure was reduced below 4 inches of mercuryabsolute within a few minutes and before reimposition of atmosphericpressure.

The actual values of the variables in the cooklug-pulling cycles of thismethod depend on the condition and type of corn grits being used as wellas the degree of pufflng desired.

The resulting vacuum pufied corn grit has a volume of from about 6 to 10times the original grit as determined by cup weights. Put conversely,the specific gravity as determined from cup weight is from about 10% to16%% of the specific gravity of the original corn grit particles. Theshape of the original corn grit is maintained, although greatlyenlarged. On cross-section, the vacuum puffed corn grit has asubstantially pure white interior and the interior cells are apparentlyuniformly expanded, there being but a few small cavities present. Theouter surface surrounding the interior portion is comprised of a thinlayer having many minute cavities substantially uniformly distributedtherethrough. This outer surface is not case hardened and issubstantially free of any surface splitting.

Examples of applying the method of this invention to corn, andparticularly corn grits, are:

Example 29 No. 4/5 com grits (20 pounds) were placed in the steamchamber and the pressure reduced to about 0.2 inch of mercury absolutefor 2 minutes, the grits being at a temperature of not less than 40 F.,to remove substantiall all of the noncondensable gases. The grits werenext steamed to a pressure of 100 pounds per square inch gauge in 5minutes accompanied by continual purging of the steam, and then firedinto the expansion chamber which was at a pressure of 0.2 inch ofmercury absolute. Evacuation of the expansion chamber was continuedduring the pull until the grits were cold set.

Example 30 No. 4/5 com grits (20 pounds) were treated in the same manneras in Example 29. except that in the cooking and pulling cycles thegrits were steamed to 100 pounds for 3% minutes, and then fired into theexpansion chamber.

Example 31 No. 4/5 com grits (20 pounds) were treated in the same manneras in Example 29, except that in the cooking and pulling cycles, theywere steamed to 90 pounds per square inch gauge in 2 minutes and thenfired into the expansion chamber.

Example 3'2 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pulling cycles,they were steamed to 95 pounds per square inch gauge in 2 minutes 15seconds, held there for 1 minute, the steam pressure quickly reduced topounds per square inch gauge, and then the grits were fired into theexpansion chamber.

Example 33 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and puffing cycles,they were steamed to pounds per square inch gauge in 127 seconds, heldthere for 1 minute, the steam pressure reduced quickly to 60 pounds persquare inch gauge, and then the grits were fired into the expansionchamber.

Example 34 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pufling cycles,they were steamed quickly to 95 pounds per square inch 17 gauge, heldthere for 1 minute, the steam pressure was quickly reduced to 60 poundsper square inch gauge, and then the grits were fired into the expansionchamber.

Example 35 No. 4/5 corn grits (5 pounds) were treated in the same manneras in Example 29, except that the cooking and pulling cycles, they wererapidly steamed to 95 pounds per square inch gauge, held there for 1minute, the steam pressure was quickly reduced to 60 pounds per squareinch gauge, and then the grits were fired into the expansion chamber.

Example 36 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pulling cyclesthey were steamed to 75 pounds per square inch gauge in 4 minutes, heldthere for 1 minute, the steam pressure was quickly reduced to 70 poundsper square inch gauge, and then the grits were fired into the expansionchamber.

Example 37 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pulling cyclesthey were steamed to 80 pounds per square inch gauge in 4 minutes, heldthere for 2 minutes, and then the grits were fired into the expansionchamber.

Example 38 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pufiing cyclesthey were steamed to 80 pounds per square inch gauge in 4 minutes, heldthere for 4 minutes, the steam pressure was quickly increased to 100pounds per square inch gauge, and then the grits were fired into theexpansion chamber.

Example 39 No. 4/5 corn grits r20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pufllng cyclesthey were rapidly steamer to '75 pounds per square inch gauge, heldthere for 8 minutes, and then the grits were fired into the expansionchamber.

Example 40 No. 4/5 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pufiing cyclesthey were steamed to 70 pounds per square inch gauge in 4 minutes, heldthere {or 7 minutes, and then the grits were fired into the expansionchamber.

Example 41 No. 8/10 corn grits r20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pulling cyclesthey were steamed to 95 pounds per square inch gauge in 1 minute 55seconds. held there for 1 minute, the steam pressure was quickly reducedto 60 pounds per square inch gauge, and then the grits were fired intothe expansion chamber.

Example 42 No. 8/10 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and puffing cyclesthey were steamed to 95 pounds per square inch gauge in 140 seconds,held there for 1 minute, the steam pressure was quickly reduced to 60pounds per square inch gauge, and then the grits were fired into theexpansion chamber.

Example 43 No. 8/10 corn grits (20 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pufling cyclesthey were rapidly steamed to 95 pounds per square inch gauge, held therefor 1 minute, the steam pressure was quickly reduced to 60 pounds persquare inch gauge, and then the grits were fired into the expansionchamber.

Example 44 Example 45 No. 8/10 corn grits (20 pounds) were treated inthe same manner as in Example 29, except that in the cooking and pufiingcycles they were steamed to 75 pounds per square inch gauge in 4minutes, held there for 1 minute, the steam pressure was quickly reducedto pounds per square inch gauge, and then the grits were fired into theexpansion chamber.

Example 46 No. 8/10 corn grits (17 pounds) were treated in the samemanner as in Example 29, except that in the cooking and pulling cyclesthey were steamed to pounds per square inch gauge in 4 minutes, heldthere for 2 minutes, the steam pressure was quickly reduced to 60 poundsper square inch gauge, and then the grits were fired into the expansionchamber.

Example 47 No. 4/5 corn grits (20 pounds) were placed in the steamchamber and steamed to a pressure of 75 pounds per square inch gauge in4 minutes accompanied by continual purging of the steam, held there for2 minutes, the pressure was rapidly decreased to 60 pounds per squareinch gauge, and then the grits were fired into the expansion chamberwhich was at a pressure of 0.2 inch of mercury absolute. Evacuation ofthe expansion chamber was continued during the pufl until the grits werecold set.

The vacuum puffed corn grits from Examples 29 to 4'7 were verysatisfactory having the above described characteristics.

The present process instantaneously cools the product to a lowtemperature because of the expansion into a low absolute pressure. Thisprevents deterioration which would otherwise be caused by the puflingtemperature as well as helping to cold set or gel the walls so that theywill not collapse upon reimposition of atmospheric conditions.

The products are preferably dried under the pufling vacuum withoutre-exposure to air. Normally a final moisture content of about l -9% issuitable for wheat. It is generally desirable to be below the normalequilibrium moisture content of the material in all cases. This usuallymeans a drop of about 3% in the drying operation. Drying is preferablyaccomplished by rediant heat under the vacuum.

The products may be dried by other mean&- as by oven drying. Oven dryingproduces case hardening and some toasting. For some purposes a slightcase hardening and toasting are suitable and may be desirable. The casehardening markedly slows down absorption of aqueous liquids.

As an instance of the applicability of the procass to the preparation ofa pre-cooked cereal having the ability of cooking prompt y. reference ismade to the application of Carmen and Allison, Serial No. 299,496, fliedJuly 17, 1952. That case primarily relates to a pre-cooked rice having aweight per quart of about 28.5% to 60% of the original material.

The particular conditions of the presently claimed process adapted forthe production of pro-cooked rice and other cereals are the invention ofCarmen and Allison described in the other copending applicationsreferred to. That process and those products are, however, likewisewithin the generic concept of the present invention.

The present process not only produces puffed materials which cannot beduplicated by any other process of which I know, but it has a wide rangeof adaptability to produce various characteristics. The process may beused to produce materials which are not case hardened. On the other handby appropriate treatment, the products may be prepared so that they arecase hardsued, the operator having a selectivity which was notcharacteristic of any other process.

Likewise, the present pulling process is the only one which produces aproduct free from scorched appearance or taste. On the other hand, ifdesired, the products may be pre-toasted or aftertoasted or crisped toprovide whatever taste is desired and may be obtained by proper heattreatment,

Likewise, as the present process retains the nutritive value of thematerials beyond that obtainable by known processes.

In the treatment of tobacco. green hands of bright tobacco were severedso that one portion consisted of the butts cut oil about five inchesfrom the end and the remaining portion consisted of the leaves abovethat point. The leaf portions were placed in the pressure or steamchamber and the pressure in this chamber reduced to a high vacuum ofabout 0.1 inch of mercury absolute. Steam was then admitted to bring thepressure to about 3 to 5 pounds gauge. The steaming was at such a ratethat the total time of steaming above zero gauge was about two minutesand not more than one minute at five pounds. The conditions just givenare for bright tobacco. Burley will stand a more severe handling withoutaffecting the leaves. During the steaming operation, a bleed linecommunicating with the steam chamber was left open to avoidcondensation. The pressure was suddently reduced by opening of thetriggered door of the explosion or expansion chamber, which chamber wasmaintained at a pressure 01' about 0.2 inch of mercury absolute. Thepressure in this chamber was not permitted to rise above approximately 2inches of mercury absolute.

The butts were placed in the pressure chamber. subjected to the highvacuum and then steamed. For bright tobacco, the steaming operation wascarried on at from six to eight pounds gauge, the time over zero poundsgauge and the time at maximum pressure being not y 20 municating withthe steam chamber was left open during steaming. The butts were thenexploded under substantially the same conditions as the leaves, but werekept separated therefrom.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom. as modifications will be obvious to those skilled in the art.

I claim:

1. The method of putting cereals which comprises freeing a cereal fromair and replacing the air with an atmosphere of steam, cooking thecereal for a period sufllcient to soften the cell walls and adapt themfor pufling, then subjecting the cereal to a sudden change from a highsuperatmospheric pressure to a low sub-atmospheric pressure whereby itis puffed.

2. The method as set forth in claim 1 in which the cereal is cookedunder a pressure of steam of approximately 10 to 40 pounds per squareinch gauge.

3. The method as set forth in claim 1 in which the cereal is cookedunder a pressure of steam of approximately 10 to 30 pounds, and thepressure thereon is then rapidly increased to a pressure in excess ofpounds per square inch, following which the product is immediatelypufl'ed.

4. The method as set forth in claim 1 in which the product is rice, andis cooked for a period of 5 to 7 minutes at a pressure of 20 pounds persquare inch gauge.

5. The method as set forth in claim 1 in which the product is rice. andis cooked for a period of 5 to 7 minutes at a pressure of 20 pounds persquare inch gauge, and the pressure is then increased to approximatelypounds per square inch gauge within less than 1 minute.

6. The method which comprises cooking a oereal in an atmosphere ofsteam, suddenly reducing the pressure below 8 inches of mercury absoluteto puff the cereal, and then drying the pulled cereal under thesub-atmospheric pressure.

'7. The method as set forth in claim 6 in which the drying isaccomplished while supplying heat to the material.

8. The method which comprises puffing a food liquid explodes into a linemist and penetrates the food product.

9. In the pulling of cellular materials, the steps of heating thematerial in the presence of moisture to produce a super-atmosphericsteam pressure thereon and then pulling the product into a maintainedvacuum sufliciently low to cold set the product by evaporation ofmoisture from and consequent cooling or the product and reimposingatmospheric pressure upon the product while in cold set condition.

10. The process of claim 9 in which the pulling operation is carried outas a batch process, the pulling being into a vacuum which. is initiallyat substantially absolute zero pressure and which rises during thepulling operation to a point not above an average pressure of 4 inchesof mercury absolute.

11. The process of claim 9 in which the putting mor than n inut h mm m 1operation is carried out as a batch process, the

pufling being into a vacuum which is initially at substantially absolutezero pressure and which rises during the pufllng operation to a pointnot above an average pressure of 2 inches of mercury absolute.

12. The method oi claim 9 in which the product is dried after thepufling operation is complete but before reimpositlon of atmosphericpressure.

13. The method of claim 9 in which the temperature of the product isreduced below 100' F. before reimposition of atmospheric pressure.

14. The method of claim 9 in which the temperature of the product isreduced below 50 F. before reimposition of atmospheric pressure.

15. The method of claim 9 in which the tem perature of the product isreduced below 150 F. before reimposition of atmospheric pressure.

16. A cold set, vacuum pulled cereal produced by the process of claim 9.

22 17. A cold set, vacuum pufled rice product produced by the process ofclaim 9.

18. A cold set, vacuum puii'ed cellular material produced by the processof claim 9.

JOHN M. BAER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,933,158 Bohn et a1. Oct. 31, 1933 2,246,528 Musher June 24,1941 2,261,456 Warren Nov. 4, 1941 2,278,464 Musher Apr. 7, 19422,295,116 Kellogg Sept. 18, 1942 2,358,250 Rogers Sept. 12, 19442,438,939 Ozal-Durrani Apr. 6, 1948 FOREIGN PATENTS Number Country Date494,085 Great Britain of 1937

1. THE METHOD OF PUFFING CEREALS WHICH COMPRISES FREEING A CEREAL FROMAIR AND REPLACING THE AIR WITH AN ATMOSPHERE OF STEAM COOKING THE CEREALFOR A PERIOD SUFFICIENT TO SOFTEN THE CELL WALLS AND ADAPT THEM FORPUFFING, THEN SUBJECTING THE CEREAL TO A SUDDEN CHANGE FROM A HIGHSUPERATMOSPHERIC PRESSURE TO A LOW SUB-ATMOSPHERIC WITHIN A SECONDARYBATTERY.